Recording device for sound on films



'SUBSTWUTE FUR MISSING XR April 13, 1937.

J. c. FARDON RECORDING DEVICE FOR SOUND ON FILMS Filed Nov. 23, 1934 SEARCH ROOM 2 Sheets-Sheet l INVENTOR.

John C. Fardon.

ATTORNEYS.

April 13, 1937.

J. c. FAfiDON 2,077,102

RECORDING DEVICE FOR SOUND ON FILMS Filed Nov. 25, 1934 2 Sheets-Sheet 2 maww ATTORNEYS.

INVENTOR.

* Join; C Faz don. I

Patented Apr. 13, 1937 UNITEB STATES PATENE' @FFHCE 7 Claims.

My invention relates to a device for producing a record of sound upon a sensitized surface, the record being in the form of a line of a general direction traced by the movement of a film past a recording point and varying, in accordance with the sound which it is desired to record, in a direction transverse to its general line of movement. Such record will, in a negative film for example, comprise a dark sound line upon a light or clear ground, and in the positive film will comprise a clear or low density sound line upon an opaque or high density field. The line itself, by which the sound is recorded, is in the nature of an oscillograph line, although the response can be controlled in any way desired.

This type of sound record is of particular utility in a method and with means for the production and translation of sound records suggested by George Sperti, and forming the subject matter of a co-pending application in his name entitled Methods of recording and reproducing sound on film, filed Nov. 23, 1934, Serial No. 754,505; but it will be clear that my invention has applications not confined to the motion picture field, but will be useful in recording electrical or mechanical vibrations other than those of sound, and, without limitation, may be used, for example, in recording upon a moving sensitized surface, variations over a period of time, of any physical quality which may be converted into electrical impulses or mechanical movements. I shall, however, describe my invention as a device for recording speech and music upon motion picture films, it being understood that this is an exemplary embodiment only of my invention.

fI'he fundamental objects of my invention are to provide a recording device and method which are simpler and cheaper than those heretofore suggested. In the following of my invention, it is not necessary that the intensity of a light source used in recording be varied at all; and in general, sporadic variations will not be of great consequence, so far as the final record is concerned, unless these variations are of considerable degree. It is an object of my invention to avoid the use of reflective oscillatory means and the necessity of optical means for focusing a beam of light on a film or sensitized surface in a small spot of controlled size. It is also an object of my invention to provide means and a method whereby it is not necessary to hold a film or sensitized surface exactly at the focus of an optical system during the whole of its movement past the recording point. It is an object of my invention to provide means and a method whereby shielding of light is both not so necessary and more easily accomplished where necessary.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that method and by that certain construction and arrangement of parts of which I shall now describe the aforesaid exemplary embodiment. Reference is made to the drawings wherein- Figure 1 is a plan view with parts in section, of an apparatus suitable for carrying on my invention.

Figure 2 is an elevational view, with parts in section, of the same apparatus Figure 3 is a perspective view of the end of a quartz rod having a particular shape.

Figure 4 is a View of a type of sound record which may be made thereby.

Figure 5 is a view of a piece of motion picture film with such a sound record thereon.

Figure 6 is a vertical sectional view of an arrangement for producing parallel beams in a narrow line. K

The drawings are semi-diagrammatic in character, and I have left out of them those parts which are not necessary to an understanding of the invention herein involved, and which may readily be supplied in known ways by those skilled in the art.

In the making of an oscillograph-type record, instead of providing a source of light in an oscillograph including a vibrating mirror and means for focusing the light through the mirror into a spot of the desired dimensions upon the moving film, which provision would entail both a serious light shielding problem and the necessity of maintaining the moving film always at the exact focus of the optical system, I provide a source of light and a quartz rod which is tapered to a point of approximately the area of the desired spot. It is known that quartz pencils have the property of causing light introduced into the pencil at one end thereof, to follow the convolutions of the pencil; and this enables me to use a bent quartz rod. While not a limitation upon my invention. the bending of the quartz rod is of importance from a constructional standpoint; and the particular embodiment which I shall describe employs a bent quartz rod. The point of the quartz rod will preferably be cut off perpendicular to its close to the point of the rod, moving the point of the rod transversely to the path of movement of the sensitized surface in a way determined by the sound waves or other impulses which it is desired to record. The film may move toward or away from the point of the quartz rod over a distance comparable to the vibration which might be expected in a film in moving it in a straight gate without appreciably affecting the quality of the record. Hence, the means hitherto employed in the art for moving the sound track portion of a film accurately past the recording point need not be employed, although of course they may be employed if desired.

In the figures, I have indicated at I a strip of film moving longitudinally and propelled by any suitable means readily understood by those skilled in the art. This is a film upon which it is desired to produce sound records; and for this purpose I have indicated at 2 a quartz rod of small dimensions. It is tapered to the point aforesaid at one end, as shown at 3, and preferably the other end of it, being much larger than the point, is bent over as at 4, giving to the rod somewhat the shape of the well known tone arm of the phonograph. It will be understood, however, that other shapes and even straight rods may be employed, the particular shape of the rod herein disclosed being advantageous from a constructional standpoint. The point of the rod approaches a face of the film I very closely as aforesaid.

The rod may be mounted as shown, in the top of a container or housing 5, the end of the rod communicating optically with the interior of the casing. The rod may be rotatably mounted in the collar 6 on the casing, or it may be solidly mounted therein, the elasticity of the rod per mitting motion of the pointed end 3 thereof, though the other end of the rod cannot move. Where this is done, the rod itself may be employed as the centering device for an electromagnetic or electrodynamic driving motor, providing the dimensions of the rod are such that it does not have a natural period of vibration within the range of those vibrations which it is desired to record.

Within the casing 5 I mount a source of light I. Preferably, though not necessarily, this source of light may be equipped with condensers 8 and 9, and a spherical reflector It], so as to deliver as much of the light from the source as possible to the rod 2. The casing 5 of course, serves to shield associated parts from light from the source I. Preferably no light is permitted to leave the casing excepting through the quartz rod 2.

The device as thus far described will be operative to trace a continuous line of light of the desired width upon the moving film l, and it may be employed without further mechanism for the purpose of producing the control record contemplated in the system of the co-pending application of Sperti, to which reference has been made. Where it is desired to record sound or other vibrations or qualities, the pointed end of the quartz rod will be caused to move in accordance with variations of the sound or other quality in a direction substantially transverse to the longitudinal axis of the film i. This is easily accomplished by connecting the quartz rod mechanically to a mechanical element which moves in accordance with the vibrations to be recorded. When recording sound, it would be possible to connect the quartz rod 2 directly with a diaphragm or other device picking up sound waves from the air; but it is more convenient and eifective, of course, to employ some sort of electromotive driving device. It is an advantage of my invention that the recording elements thus far described may be directly coupled to an electromotive driving means in the nature of a loud speaker motor, either of the magnetic or dynamic varieties. This makes for a great simplification of apparatus, as will be clear. The loud speaker motor will, of course, be driven by current varying in accordance with the sound waves or the like, and amplified or otherwise controlled as desired.

I have shown in the drawings a loud speaker motor of the so-called dynamic type having a field structure II and a, field winding l2, which may be and preferably will be energized by direct current. The voice coil support of the speaker motor is indicated at 13, and bears the voice winding l4, all as is well known in the art. The voice coil support may be connected mechani cally as by means of a rod IE, or a rod and link construction, with a collar l6 near the pointed end of the quartz rod 2. Current varying in frequency or direction in accordance with the sound which it is desired to record, will be im pressed upon the voice coil l4 through the voice coil leads H and I8. The voice coil and its support, therefore, will move in and out with respect to the coil structure H in accordance with these vibrations, and. the mechanical connection between the voice coil support and the quartz tube will cause the tube to vibrate in accordance therewith. The amplitude of the vibrations of the quartz tube may be controlled in any suitable manner. With either a straight or bent tube fixed or merely pivoted at one end, the amplitude of vibration may be controlled by positioning the collar l6 closer to or further away from the pointed end of the quartz rod. Otherwise the vibrations may be controlled in amplitude by suitable linkage connections between the moving element of the driving motor and the quartz tube. It will be understood that other types of driving motor may be substituted for the one specifically illustrated in the drawings; and further, that the motor, the rod, and the means for supplying light to the rod, may be mounted in the recording head upon any suitable supporting means.

It is possible to grind upon the end of the rod 5 lens surfaces for different effects. Convex surfaces so ground will tend to focus the rays of light passing through the rod at a point or line ahead of the rod end. Consequently instead of using a very narrow tip on the rod spaced quite closely to the film, it is possible to interspace the end of the rod from the surface of the film and to either bring the light to a focus upon the surface of the film, or produce a relatively high intensity, but very narrow beam of parallel light impinged upon the surface of the film. If the rays are truly parallel and the dimensions of the beam are proper, variations in the distance of the film from the end of the rod, such as might occur in a straight gate, will not affect the recording. Thus, I have shown in Figure 6 a sectional view of the end of a rod I1, having a convex surface ground and polished thereon as at Ill. The rays of light are indicated by dotted lines and come to a focus at about the center of a concave lens 19. The curvature of the face or faces of this lens may be so proportioned to the curvature of the end E8 of the rod, that the beam of light passing therethrough is parallel. It will usually be advantageous to make the lens [9 a cylindrical lens, so that bodily movement of the end of the rod I! will not have an appreciable effect upon the dimensions of the spot of light formed thereby.

It is possible using my apparatus, to make sound record which while based upon the oscillograph principle, nevertheless act as sound records of ordinary form. I have shown in Figure 3, a quartz rod which is relatively broad in horizontal dimension. This rod is indicated at 20. Its end is ground to present a, convex cylindrical surface 2|, serving to bring the rays of light transmitted through the rod to a focus as at 22. The film may either be maintained at this Iocal line or a concave lens may be used to provide a parallel narrow beam after the manner illustrated in Figure 6. The cylindrical surface of the end of the rod will bring the light rays to focus in a line rather than in a point. If this line impinges upon the surface of a film at the sound track portion, and if the rod is maintained stationary there, variations in the light transmitted through the rod will give a sound track recording of the variable density type. This, however, involves the problem of varying the intensity of the light source with the sound waves; and while such a system is included within the scope of my invention, yet I prefer to move the end of the rod as aforesaid, so as to make a sound record without varying the intensity of the light source. I have shown in Figure 4 a type of oscillograph record which might be made by the rod illustrated in Figure 3. This oscillograph record varies its lateral position in accordance with the sound waves which it records, and the recording is in the form of a broad line, black upon the negative and light or translucent in the positive. If however but a portion of this record, i. e. the record 23 in Figure 4 is scanned, say that portion which lies between the dotted lines 24, it will be clear that the record will act as an ordinary record of the variable area type, and can be scanned as such. In using the rod of Figure 3 in making this type of record, one portion of the record may be allowed to extend into the sprocket holes or elsewhere on the films, since only a portion of the record is required for scanning purposes. I have illustrated this in Figure 5 where I have shown a film 25 having sprocket holes 2'5. Image frame spaces are indicated at 21. The sound track may be considered as that portion of the film lying between the left-hand sprocket holes and the image frame and the area being scanned at any one instant may be indicated by the rectangle 28. It is clear that the portion of the sound record which extends into the sprocket holes is the unused portion, approximately half the record being scanned in the area 28 as though it were the ordinary variable area type of record.

It will further be understood that in the place of quartz. I may employ other translucent media having the same property of diverting beams of light, or translucent tubes or rods to which a similar property has been imparted, by silvering the surfaces thereof or otherwise. Modifications may be made in my invention without departing from the spirit thereof.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. A recording device comprising a rod of translucent material bent intermediate its ends so that one end lies substantially at a. right angle to the other one of said ends, being pointed, a casing, said unpointed end being mounted on said casing, a source of light in said casing and in optical connection with said end of said rod, and a loud speaker motor having a mechanical connection with said rod near the other end thereof.

2. A recording device comprising a translucent elastic rod pointed at one end to substantially the width of the desired sound record, means for introducing light into the other end of said rod, a motor of the type employed for converting electrical vibrations into sound vibrations, said motor having a moving part, and a connection between said moving part and said rod, one end of said rod being fixed and said rod serving by its elasticity as a centering device for said moving part of said motor.

3. A means for making a variable area type of record on a photographic film comprising a quartz rod one end of which is tapered to a relatively narrow edge, said edge being formed to a cylindrical shape to provide a lens, means for introducing light into one end of said rod, and means for moving the other end of said rod substantially in the direction of the axis of said cylindrical edge in accordance with the variations of a quality which it is desired to record.

4. In a sound recording device, a quartz rod one end of which is tapered to a relatively narrow edge, said edge being formed to a cylindrical shape to provide a lens, means for introducing light into the other end of said rod so as to cause said light to issue from said narrow end, and an electromotor device having a part moving in accordance with audible variations, and a mechanical connection between said motor and said quartz rod.

5. In a recording device, a casing, a source of light in said casing, a translucent rod one end of which is tapered to a relatively narrow edge, said edge being formed to a cylindrical shape to provide a lens, the other end of said rod being connected with said casing and in optical connection with the source of light therein, and means for moving said narrow end of said rod in the direction of the axis of said cylindrical edge.

6. In a recording device, a casing, a source of light in said casing, a translucent rod one end of which is tapered to a relatively narrow edge, said edge being formed to a cylindrical shape to provide a lens, the other end of said rod being connected with said casing and in optical connection with the source of light therein, and means for moving the narrow end of said rod in the direction of the axis of said cylindrical edge, said means comprising a loud speaker motor and amechanical connection between a moving part thereof and said rod.

7. In a recording device, a casing, a source of light in said casing, a translucent rod one end of which is tapered to a relatively narrow edge, said edge being formed to a cylindrical shape to provide a lens, the other end of said rod being connected with said casing and in optical connection with the source of light therein, and a cylindrical plano-concave lens adapted to modify the light rays emerging from said narrow end to produce a thin band of parallel rays, and means for moving said narrow end of said rod in the direction of the axis of said cylindrical edge.

JOHN C. FARDON. 

